, Volume 12, Issue 3, pp 393-402

Deposition of nanoparticle suspensions by aerosol flame spraying: Model of the spray and impact processes

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Abstract

Aerosol flame spraying (AFS) combines the atomization of a colloidal suspension with the lateral injection of the aerosol in a flame. The aerosol droplets are partially dried when crossing the flame and then deposited as a coating onto a substrate. Afterwards, the coating is consolidated by heat treatment without extensive grain growth. In this paper a model of the trajectories, acceleration and vaporization of the droplets is used to predict the impact conditions of the in-flight dried droplets, as well as their size and water content when they impinge onto the substrate. From these calculations and the hydrodynamic properties (viscosity, surface tension, contact angle) of the suspensions, the morphology and size of the lamellae deposited on the substrate are determined by using classic impact models. In spite of the complexity of the mixing of the suspension spray with the flame and the diversity of the thermal histories of the droplets, the observation of the latter after impact shows that the results of the model are quite consistent with measurements. The relationship between droplet impact parameters and coating formation is discussed.